Cs3Bi2Br9 QDs/BiOBr heterojunction photoelectrochemical biosensor with APE1 enzyme-driven bipedal DNA walker signal amplification for miRNA-320d detection

Abstract

Background: MicroRNAs (miRNAs), as pivotal biomarkers, demonstrate critical significance in early cancer diagnosis through their sensitive detection. An ultrasensitive photoelectrochemical (PEC) sensing platform for miRNA-320d detection was developed by integrating apurinic/apyrimidinic endonuclease 1 (APE1) enzyme-driven bipedal DNA walker amplification strategy.

Results: The platform employed a Cs₃Bi₂Br₉ QDs/BiOBr Z-scheme heterojunction as the photoactive material, which generated a robust anodic photocurrent. Upon immobilizing alkaline phosphatase (ALP)-conjugated gold nanoparticles carrying apurine/pyrimidine (AP) site-modified L1 (ALP-Au NPs-L1) probes on the heterojunction surface, catalytic hairpin assembly (CHA)-generated 3D bipedal DNA walker walked in the presence of miRNA-320d, hybridizing with L1 to form duplex structures. The APE1 enzyme then selectively cleaved these duplexes, triggering the release of ALP-Au NPs from the electrode surface. This spatial separation deactivated the catalytic capacity of ALP, inducing a pronounced photocurrent attenuation. By synergizing the exceptional PEC performance of the Cs₃Bi₂Br₉ QDs/BiOBr heterojunction, specific recognition and efficient cleavage of APE1 enzyme, and 3D walker-mediated signal amplification, this platform achieved ultrasensitive miRNA-320d detection with a detection limit of 0.1 fM and a linear range spanning 1 fM to 1 nM.

Significance: This study established novel conceptual frameworks for implementing emerging perovskite materials in PEC biosensing platforms targeting microRNA detection.

Keywords: APE1 enzyme; DNA walker; MicroRNA-320d; Perovskite quantum dots; Photoelectrochemical biosensor.